1. Field of the Invention
The present invention relates to processes for making the compounds of formula I which comprise a dehydrohalogenative coupling of hydrochlorosilanes of formula II with organic halides of formula III in the presence of Lewis base catalyst. EQU R.sup.3 CH.sub.2 SiR.sup.1 Cl.sub.2 (I) EQU HSiR.sup.1 Cl.sub.2 (II) EQU R.sup.2 CH.sub.2 X (III)
In formulas I and II, R.sup.1 represents a hydrogen, chloro, or methyl; in formula III, X represents a chloro or bromo; in formula III, R.sup.2 can be selected from the group consisting of a C.sub.1-17 alkyl, a C.sub.1-10 fluorinated alkyl with partial or full fluorination, a C.sub.1-5 alkenyl groups, a silyl group containing alkyls, (CH.sub.2).sub.n SiMe.sub.3-m Cl.sub.m wherein n is 0 to 2 and m is 0 to 3, aromatic groups, Ar(R').sub.q wherein Ar is C.sub.6-14 aromatic hydrocarbon, R' is a C.sub.1-4 alkyl, halogen, alkoxy, or vinyl, and q is 0 to 5, a haloalkyl group, (CH.sub.2).sub.p X wherein p is 1 to 9 and X is a chloro or bromo; or an aromatic hydrocarbon ArCH.sub.2 X wherein Ar is C.sub.6-14 aromatic hydrocarbon and X is a chloro or bromo. in formula I, R.sup.3 is the same as R.sup.2 in formula III and further, R.sup.3 can also be (CH.sub.2).sub.p SiR.sup.1 Cl.sub.2 or ArCH.sub.2 SiR.sup.1 Cl.sub.2 when R.sup.2 in formula III is (CH.sub.2).sub.p X or ArCH.sub.2 X, because of the coupling reaction of X with the compound of formula II.
2. Description of the Prior Art
In 1968, Benkeser and Smith reported the reduction of carbon tetrachloride to chloroform by using a 1:1 mixture of trichlorosilane and tertiary amine as reducing agents (Benkeser, R. A.; Smith, W. E. J. Am. Chem. Soc. 1968, 90, 5307). They proposed that the amine-catalyzed reduction of carbon tetrachloride to chloroform proceeded via the formation of (trichloromethyl)trichlorosilane by the dehydrochlorinative coupling reaction between the carbon tetrachloride and trichlorosilane, and subsequent cleavage of the carbon-silicon bonded species by ammonium chloride to give chloroform and tetrachlorosilane. In 1969, Benkeser and co-workers also reported that benzyl chloride and benzyl chlorides could be silylated with trichlorosilane-tertiary amine 1:1 mixture to give the corresponding trichlorosilyl substituted products by the dehydrochlorinative coupling reaction (Benkeser, R. A., Gaul, J. M.; Smith, W. E. J. Am. Chem. Soc. 1969, 91, 3666).
In 1975, Furuya and Sukawa reported allytrichlorosilane could be prepared in high yield by a coupling reaction of allyl chloride with a 1:1 mixture of trichlorosilane and tertiary amine in the presence of copper chloride as a catalyst (Furuya, N.; Sukawa, T. J. Organometal. Chem. 1975, 96, C1).
Recently, Corriu and co-workers reported that the reaction of chloroform with trichlorosilane in the presence of excess tributylamine gave bis(trichlorosily)methane and tris(trichlorosilyl)methane (Corriu, R. J. P.; Granier, M.: Lanneau, G. F. J. Organometal. Chem. 1998, 562, 79). These reports suggest that a chloroalkyl group containing organic compounds and organosilanes having Si-H bonds could undergo the dehydrochlorinative coupling reaction with trichlorosilane in the presence of an organic base.
The dehydrochlorinative coupling reaction is a novel method of forming silicon-carbon bonds useful for the synthesis of organosilicon compounds. Although the dehydrochlorinative coupling reaction of activated alkyl chlorides such as benzyl chloride or allyl chloride have been reported, the coupling reaction of unactivated alkyl chlorides with trichlorosilane has never been reported. In the previously reports, tertiary amine was used in excess, more than the stoichiometric amount respect to alkyl chloride. The tertiary amine used is a hydrogen chloride scavenger rather than a catalyst. Since the ammonium salt obtained from the tertiary amine and hydrogen chloride have to be neutralized to recycle the amine, it would be too costly to be utilized on an industry scale. It is necessary to find a way to reduce the usage of the amine or find another effective catalyst to apply the coupling reaction for industrial purposes.
The present inventors have discovered that a coupling reaction of alkyl halides and hydrochlorosilanes in the presence of various tertiary amines or tertiary phosphines as a catalyst proceeded to give the corresponding coupled products by liberating hydrogen halide as a gas. The dehydrohalogenative coupling reaction can be applied to not only the activated alkyl halides such as benzyl chloride or allyl chloride, but also to the unactivated alkyl halides such as n-alkylhexyl chloride or haloalkyl substituted organosilicon compound. Suitable amine catalysts include, but are not limited to triethylamine, tri-n-propylamine, tri-n-butylamine, N,N,N',N'-tetramethylethylenediamine, pyridine, N,N-dimethyltoluidine, N-alkylpyrrolidine. Suitable phosphine catalysts include, but are not limited to tributylphosphine, triethylphosphine, tricyclohexylphosphine, triphenylphosphine, bis(diphenylphosphine)methane, 1,2-bis(diphenylphosphine)ethane, and phosphine coordinated transition metallic compounds such as tetrakis(triphenylphosphine)palladium, tris(triphenylphosphine)rhodium chloride, or tetrakis(triphenylphosphine)platinum.